


Open Circuits

by Strings (fangirlgeekout)



Category: Supernatural
Genre: Alternate Universe - Future, Alternate Universe - Human, Coming Untouched, Fluff, M/M, Robotics, Sensation Play, Sensuality, Tickling, Ticklish Castiel, electrostimulation I guess?
Language: English
Status: Completed
Published: 2016-05-14
Updated: 2016-05-14
Packaged: 2018-06-08 04:52:23
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,432
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/6839815
Author URL: https://archiveofourown.org/users/fangirlgeekout/pseuds/Strings
Summary: <blockquote class="userstuff">
              <p>Synthetic limbs have always been normal for Castiel, but Castiel’s normal seems to be different from everyone else’s. At least it makes for some interesting bedroom experiences. (Kink: tickling)</p>
            </blockquote>





	Open Circuits

**Author's Note:**

> Supernatural Kink Big Bang 2016 – group #16, mini bang  
> Artist: [@topieornottopie](http://topieornottopie.tumblr.com/)  
> Art post: [here](http://topieornottopie.tumblr.com/post/144351355089/art-i-made-for-the-fic-open-circuits-by)  
> Author: [@wordstrings](http://wordstrings.tumblr.com/)
> 
> Rebloggable on Tumblr [here](http://spnkinkbb.tumblr.com/post/144362262352).

Castiel careened through the living room on stubby legs. He dove under the table, whimpering, and drew himself into the smallest shape he could. His left arm folded in tightly to his chest, the exposed wiring digging into his stomach as he curled his knees up to protect it from the pain that was sure to come.

“Quit running, would you?”

His older brother’s voice was exasperated. Socked feet paced into sight around the corner and stopped.

Cas couldn't help the sound of upset that cracked from his throat. Warm tears spilled down his cheeks. Cleaning was bad; cleaning _hurt_. He clutched his arm and shuddered at the sensation of his fingers digging down between the acrylic bones. They were bright primary blue.

-

The defect itself was not all that uncommon, the doctors had said, though the apparent severity wasn’t often seen. _Amniotic band constriction resulting in congenital amputation_. Extremities would get caught up in fibrous tissue, restricting the blood flow. But, they insisted, surgeries could take care of most functional and cosmetic issues after birth. In fact, it was often easier to remove the affected part and fit a synthetic replacement. Less developmental difficulty, less social stigma, and the computerized components were no longer so rife with glitches or associated health risks.

It was assured and reassured that complete in-utero loss of a full limb was not cause for alarm. Synthetics were commonplace, and even came in inexpensive variants that made replacement during rapid growth perfectly feasible. Complete loss of _two_ limbs – well. A synthetic arm and leg both on the same side of the body might complicate the nervous system integrations. But, really, the doctors insisted, it shouldn’t be any trouble at all.

Four years and a dozen accidents later, it might have proven itself to be a _little_ bit of trouble.

This time, it had been Gabriel’s fault, anyway. Tickle fights never ended well for younger siblings, and in Cas’ haste to escape outside, he'd snagged his arm on a weathered corner of the decking in the yard. The initial sear of pain had made Cas scream before the pseuskin receptors automatically dulled the nerve response. He'd fallen to the grass, shocked and tearful. The gash in his forearm didn't leak blood, but gaped open to the tangle of wire and plastic beneath. The damaged panel needed to be replaced.

Cas had calmed down once he was carried inside and the torn pseuskin was disconnected. Gabriel knew where to find the spares in Dad’s closet upstairs. While he rummaged, Cas was left to sit on the end of the bed and pick at his open edges. They were clean and straight, a long, neat opening where half the forearm clamshell had been removed.

He swung his legs freely and stared at the seam running down his left calf whenever it kicked up into view. The panel there had a secret smiley face drawn on the inside with purple marker. That had been Gabriel, too. It made Cas smile whenever he remembered it was there.

The rest of his body was boring. There were no secret messages written inside his organic flesh.

When Gabriel set aside the new pseuskin instead of attaching it right away, Cas stopped kicking his legs. He watched his brother’s carefully blank face as Gabriel lifted his arm and began disconnecting the other panels from it.

Dread saturated Cas’ belly. “Gabe?” he started fearfully.

“Now, Cas, don't freak out...”

His brother leaned back to put the last panel down behind him, leaving Cas’ arm bare down to the mechanics. The end of an ion wand on the bed flashed into view.

Gabriel cursed when Cas bolted.

-

There was a sigh, and the legs in Cas’ view folded down to the carpet. Gabriel’s lanky shoulders ducked low to bring him into view beneath the tabletop. He seemed to soften.

“Cassie, it's not going to hurt this time.”

Cas squirmed further away with a sob. He could see it, the ion wand his brother tried to keep palmed out of sight. The shocks it delivered were harsh and raw, and Cas didn't care if dust settled into him before the new pseuskin got fitted over his arm. Dirt abrading his elbow or wrist bearings could never be as painful as the electricity that jolted through his sensitive synthetic components, from his gel fingertips all the way up to the integration at his organic shoulder socket.

“I promise,” Gabriel soothed. “We got a new one that's better. It's a different kind than the old zapper from Uncle Raph, see?” He held the wand out in front of him. It was black like the one Cas hated, but with a matte finish, a little shorter and thinner. The two slender prongs on the end seemed molded out from the rest of it, smooth and black, and rounded instead of the sharp silver ones that sparked when they charged.

Cas still cringed and recoiled. His vision wavered, melting at the edges with freshly gathering tears.

“Here, look.” Extending one arm, palm up, Gabriel carefully touched the pronged tip of the wand to the soft organic skin of his own forearm. He didn't flinch. “Doesn't hurt. You wanna try?”

The wand was offered toward Cas.

He whined, but Gabriel looked sincere. After a moment of hesitation, Cas slowly crawled forward, keeping his arm with all its brightly-colored, vulnerable mechanisms curled close to himself. He reached out with the other hand and wrapped his small fingers around the wand’s body. It hummed almost imperceptibly, though wasn't cold like the bad wand. _But this one might be bad too._

“Clean me,” Gabriel said gently. He held his arm out, bare up to the sleeve of his worn tee.

The elbow joint was always one of the worst. Cas’ breath hitched as he tapped the wand at the skin of his brother’s inner elbow. It made a soft fizzling noise, and the hair on Gabriel’s arm lifted slowly. No sharp crack of sound, no spark, no pain. _Not bad_.

“See?”

Cas sniffled and blinked away the remnants of his tears. He habitually swiped his free wrist up under his nose – prompting a too-late grab by Gabriel.

“Gross,” his brother lamented. “Now we have to wipe your snot out of your circuits.”

 

-

Moments later, Cas was bolting again. He sprinted into his bedroom, panting for breath, hearing Gabriel’s pursuit close behind him. _Under the bed. He can't reach you there._ He threw himself to the floor and wriggled to safety beneath the low clearance.

A grip closed on his ankle.

“Do you have any idea how filthy it is under there?” Gabriel exclaimed. “Are you _trying_ to make this worse?”

Cas squealed as he was dragged back out into the light. He twisted and flailed, but his brother caught his mechanical wrist and plunged the ion wand into the wiring.

“ _No_!”

Cas’ shriek resolved into hysterical giggling. The charge shot through his conductive components, tingling intensely. A wisp of dust bunny expelled out from between the wires and drifted to the floor.

“Not my fault you're ticklish,” Gabriel smirked.

—

Castiel yelped as he stumbled over a discarded shoe. Panic surged through his chest, and he caught at the arm of the couch to keep himself upright. He threw himself forward, unbalanced flailing be damned, until his long legs were propelling him once again at pace. Rounding into the main living space, he dashed to the far side of the dining table, making the chairs clatter as he grabbed at them to check his speed. Cas whirled to face the entrance of the apartment. His breath was short with adrenaline.

The thudding footsteps of his pursuer faltered. A thump, a curse, and Cas’ brain waffled over whether the delay gave him time enough to break for the kitchen. He regretted buying the flat-pack furniture sized for tiny living spaces rather than, say, a heavy banquet table that would have taken up the entire room. That would have at least guaranteed a larger obstacle to put between himself and–

Dean came swinging around the edge of the doorframe. His eyes glinted as they pinned Cas across the tabletop.

Cas’ pulse buzzed. He swore he could feel answering electric sparks teasing beneath the panels of his left arm and leg. He feinted to one side, muscles and pneumatics tensed. But Dean didn’t mirror, or pause to calculate; he came tearing around the table in sure pursuit. Cas shouted in surprise, the sound stuttering into a laugh. He scrambled into action again and flung himself down the hall toward their bedroom.

_Getting chased into a dead end is a terrible strategic decision._

Dean’s muscular arm caught him just before the doorway, sure as a steel claw hooked around his middle. Cas managed half a gasp before strong fingers were wriggling into his stomach, digging vigorously for his laughter. His body jolted with ticklish squawking even as Dean forced him blindly forward.

“Thought you could run from me, huh?” Dean growled behind his ear.

A coherent response was hopeless, and Cas’ organic knee weakened just before his synthetic one. It sent him buckling to one side while he giggled helplessly, but Dean caught his weight with practiced reflexes. He hauled them both up and hurled Cas onto the queen mattress before pouncing over him, grinning predatorily. Cas barely gasped a breath before Dean started tickling him again, attacking his ribs with kneading that always drove him into hysterics. The rumpled comforter, already half flung to one side – because Dean insisted that bed-making was pointless if one were only going to mess it up mere hours later – provided Cas something to twist one hand into. The other grabbed erratically at Dean’s shoulder, his shirt, his hair, as Cas shrieked with laughter. The only things he didn't grab at were Dean’s tickling hands.

_Strategic decisions aren't exactly terrible if they yield the desired results._

The frenzied flipping sensation in his stomach was exhilarating. His body was utterly out of his control, whipped up into spasms of squealing laughter that wet the corners of his eyes. Dean’s keen fingers knew how to claw past his defenses and dig into his deeper center to find the chaos hidden there under layers of orderly circuit integrations.

Cas reveled in it.

He kept their kitchen impeccable. He picked up Dean’s dirty socks. He tended to the herbs he kept in little pots on the windowsills. Everything was tidy, trim, and organized.

He could have this one thing, this upheaval of all control. He chased the forcible surrender even as it chased him, with impish green eyes and a knowing smirk. When life was eighteen credit hours and thesis papers and governed-PSI grip strength, rebellion was squirming with uncontrollable laughter.

That, and what he'd come to call _recreational cleaning_.

Preferably both.

“It’s a good thing you’re into this, you know.” Dean’s fingertips choreographed a quick dance along his stomach and slipped under his shirt to work it off while simultaneously keeping Cas in stitches. “You’re so fucking adorable, I’d probably have to do this to you anyway and just deal with the title of ‘shitty boyfriend who tortures you all the time.’ But _you_ just think I’m awesome and accommodating in bed.” Cas’ shirt got tossed to the floor.

“You’re still a shitty boyfriend,” Cas wheezed, then squealed at the retaliatory raspberry his torturer blew on his bared belly.

Dean’s hand spidered up Cas’ side and under his synthetic arm, scritching at the join with his organic flesh. Cas giggled madly as the searching fingers prodded for the right spot in the seam. A press there released the edge of one panel, and Cas gasped through his laughter at the sensation of cool air leaking into the workings beneath.

“Dean...!”

It wasn’t meant to feel quite like this. When he was a child, Cas used to tell his fitters how uncomfortable it was, being opened up for maintenance, how he could feel the rasp of precision tools like the scrape of sharp metal on glass. They’d always looked at him oddly before telling him _just stay still, it’ll be over in a minute_. The elementary school med office had standard ion wands that burned, but other children didn’t have to be held down, wailing, while playground dirt was cleared from their joints. Cas’ doctors never took him seriously when he complained, so he never felt compelled to tell them how he’d started removing the pseuskin himself to try handling his own upkeep. And he certainly never told them how he’d first made himself shiver with a too-gentle touch near the piston inside his forearm.

No one knew. No one – except Dean, who had once come back to the apartment early from a cancelled class, and found Cas sprawled on the couch, panting, with wanton fingers tangled in the bare wiring of his thigh. The mortification had been absolute. At least, until Dean had asked whether he could touch, too. It had been masked as academic curiosity, but the way Dean’s eyes had darkened at Cas’ bodily response to his skimming fingertips soon threw off all disguises.

Now, Dean wore the same smirk he did when unzipping Cas’ jeans as he wiggled the released panel out from under Cas’ upper arm. It sent a rush through Cas’ bloodstream. Electric tingles raced down his arm, lighting his synthetic nerves with anticipation. One by one, Dean popped the pseuskin panels from their seats, lifting them away with hands that teased their edges and kept Cas squirming. Soon, his entire left arm was laid bare to the labyrinth of synthetics beneath.

The brush of fingers along his surface wiring was like a feather’s caress. Cas shivered, sighed, then tensed into a squeak when Dean tickled his socket joint from below.

The combination of playful and sensual touches roused something in Cas that he never thought he’d experience with a partner. The rest of the world seemed so focused on sex as a self-contained act; it had never felt that way to Cas. There was so much more outside of that, so many sensations to be had and dynamics to explore. By some twist of fortune that had Cas still trying to figure out if he’d unknowingly sold his soul at one point or another, Dean seemed to share his views. Or, at least, he was perfectly willing to indulge them.

Dean suddenly paused and sat up with a sly smile.

“Oh, I almost forgot. I got you a present.”

Cas perked up. There had been a box delivered in Dean’s name earlier in the week that he’d left untouched with the other mail, assuming it was parts needed for an engineering design course. It had disappeared with no mention of its contents, and Cas had promptly forgotten about it. He pushed himself up on his elbows to watch as Dean dove toward the side of the bed and stretched to open his nightstand drawer without getting up.

It left Dean’s socked foot jammed against Cas’ hip. Cas reached down, the whispering whir of his joints more audible without their coverings, and he swiped the gel pads of his fingers along the offending sole.

Dean flinched and huffed a laugh. He looked back over his shoulder. “Do you want this or not, Threepio?”

“That depends what it is.” Cas flicked a toe. He got kicked.

Groaning at the stretch, Dean shoved the drawer closed before scrambling back up the bed with the box Cas recognized in hand. He fished out its contents and tossed the box to the floor, then held the item aloft for Cas’ inspection. He grinned proudly.

It was no bigger than a pen, whatever it was. It looked soft to touch, like it was coated in silicone, and was tipped with half a dozen rubbery-looking little fingers. It was also pastel pink.

“Did you buy me the world’s smallest dildo?” Cas deadpanned.

Dean rolled his eyes. “No, you douche. It’s a wand.”

“It’s… _what_?”

It had been a while since Cas replaced his personal ion wand, but he was certain even the newest ones didn’t look like _that_. But when Dean’s thumb pressed on it, a familiar barely-there hum started up.

“Turns out, there’s a market for these,” Dean mused, turning the device in his hand. “Soft-touch conductor, user friendly, dishwasher safe. You’re not the only one who likes a little _Weird Science_.”

Cas reached toward it with his organic right hand, his mind buzzing with the revelation. Someone out there was like him. Several someones. He took the wand in his thumb and forefinger, almost afraid to set off its charge and ruin the fantasy he was already building around how it might feel.

His focus was snatched away to where Dean traced a fingernail down the casing of his exposed humerus. Cas groaned and his other hand dropped to the mattress, his grip on the wand loosening as his body sank into the bed. Dean’s touch was always worth all his attention, mystery wand or no. He shuddered when the fingertip skirted around his elbow joint and continued slowly down his forearm, drifting between the slender pistons, wires, and metallic bones at the core. A bristling of goosebumps spread across his shoulders and behind his neck, and he hummed, long and low.

When Dean picked up his wrist, Cas drew an anticipatory breath. The first flutter of lips over the bearings there forced his breath out in a rush. No amount of warnings about moisture issues would ever be enough to deny Cas the feel of Dean’s mouth. Warm, humid air pulsed into the workings of his wrist in time with Dean’s breath. Soft lips brushed and kissed, working their way slowly to the flexible gel sections of his palm. All the while, Dean cupped the back of Cas’ hand, fingertips absently caressing the exposed metacarpals.

A hot curl of tongue between the joints of Cas’ fingers made him gasp. Dean took the ring finger into his mouth, laving along its underside. The texture and heat of Dean’s tongue against the hinge joints and synthetic tendons was a transcendent pleasure that propelled Cas higher, higher–

Cas yelped and jerked his arm back, popping his finger out of Dean’s mouth. His eyes flew open as he recoiled to protect himself from a sudden, unpleasant prickling on his stomach.

Dean must have taken the wand from his lax grip without Cas even noticing. He held it over Cas’ midsection, its little fingers now hovering just shy of kissing the skin.

“Is it weird?” Dean asked with a grin. “I tried it earlier and thought it was weird.”

“Thanks for ruining the moment,” Cas grumbled.

“But is it?”

“Yes, it’s weird.” He dropped his arms out to his sides, mildly annoyed at having his expectations shattered without warning. “It doesn’t even-nnn... _oh_.”

All his breath petered out in a round-mouthed exhale. On organic skin, it felt a little like an uninvited insect. But when Dean moved it to his synthetics–

“ _Hnnn..._ ” Cas gulped as the head of the device trailed along his forearm wiring. It didn’t discharge all at once like a normal ion wand. It maintained a low-level flow that seemed to crawl steadily along his components, saturating them with a soft tingle that felt… _amazing_. He clenched his upturned fist and tried to breathe through the new sensations that he definitely never, ever wanted to stop.

Dean chuckled. Cas must have closed his eyes again, because he had to open them to see what Dean found amusing.

“Enjoying yourself?” His boyfriend nodded downward.

Cas glanced down and was only partly surprised by the sudden bulge in his jeans. It usually took a while for the evidence of his arousal to grow – he’d always suspected that the proximity of his hip integrations interfered – but this wand was nothing like he’d ever felt before. He was quickly becoming breathless just from the unremitting tingles. It would be easy to get completely drunk on nothing more than this.

“Dean… it’s... _ah_!”

The sparkling sensation in his forearm grew stronger by degrees as Dean manipulated the capacitive controls. Cas flexed his arm where it lay flung out from his side. Thin wrinkles of the bedsheet were getting pinched up in the open hinge of his elbow. He was vaguely aware of Dean’s free hand fumbling at his pants, then a blessed release of pressure with the sound of a zipper. But nothing down there was nearly as important as what was happening as the wand’s perfect magic traveled further up his arm, leaving a wake of glittering pleasure behind it. Cas panted through his nose and pressed his head back into the pillow.

When the wand’s pink fingers nestled into his inner elbow, Cas jerked at the unanticipated intensity. Tendrils of energy seemed to wind down through the joint, snakelike, coiling around every sensitive juncture. The sheer _thoroughness_ of the device had him open-mouthed and squirming against the sheets. He levered his head deeper into the pillow, gasping with his chin tilted high.

“O-oh God…”

He was dimly cognizant of Dean’s nose brushing his chest, lips sealing and releasing softly down his skin. A passing nibble on his side made Cas twitch; Dean quickly sought to pinpoint the spot with flicking tongue. Cas giggled despite himself. He gripped organic fingers into Dean’s hair, grasping and massaging in turn as the path of teasing licks and kisses meandered down his torso, counterpoint to the wand’s steady hum in his arm. The combined forces submerged all other senses. Cas was being sweetly drowned, and it was divine.

The sudden loss of both Dean and the wand was like being dropped into a desert. The arid emptiness along his arm felt stale. Cas whined plaintively.

But then there were hands tugging down on the open waist of his jeans, and that was worth something, so he assisted with a shimmy and kick. The air was cool on his heated skin. A heavy _flop_ of fabric indicated the jeans and boxers had met the floor somewhere near his previously discarded shirt.

Dean made an appreciative noise and rubbed a palm over Cas’ new exposure. Cas sighed and bumped his hips upward, but Dean slid over his legs to halt the motion. His weight settled on Cas’ knees.

“Stop me if you hate this,” Dean said, his voice rolling low. “But I really don't think you will.” His tongue curled along the edge of his canine as he grinned.

Dean picked up the wand and touched its humming fingers to the inner seam of Cas’ synthetic thigh.

“ _Hah_!”

Cas jolted at the foreign sensation. He quivered for a moment, his body unsure how to process it. Without exposed conductive components to scurry into, the little wand’s charge fanned out along the pseuskin. The prickle-tingle shifted as Dean fiddled with the controls. It dulled, then flared, softer around the edges, and Cas suddenly realized what Dean was going for just as the sensation resolved into a relentless tickle.

Cas arched against his boyfriend’s weight holding him down and _squealed_.

It wasn't fair at all. Dean _knew_ just how sensitive Cas’ thighs were, both organic and synthetic; how caressing and teasing them was the fastest way to get the rest of his body interested, that nuzzling and nibbling them left him breathless, and that tickling them drove him to hysterical giggling even as his hips would buck traitorously.

Both hands flew down to swat at Dean and the wand. He'd had enough self control earlier to keep the fight-or-flight instinct at bay, but it all crumbled in the wake of his built-up arousal. Cas’ left arm whirred sharply as he flailed and squeaked out laughter. Between the weight straddling his knees and Dean’s forearm across his hips to keep them from twisting, he couldn’t squirm away. Cas shrieked and giggled; Dean bit his lip in grinning concentration; the wand tickled and tickled and tickled.

And despite all of it, the heat in Cas’ core grew, tightened, sank deeper into his hips. His spine felt as though it were compressing inside like a spring being wound taut. If Dean didn't stop… didn't… stop… _oh, fuck, don't stop_.

Every inch of his body begged for more touch, more of the sensation that was too fierce but still shy of enough. The wand skimmed his inner thigh, its fingers spinning webs of fluttering energy that made him writhe and giggle merrily. Stray charges intermittently slipped between his panels at the seams and licked deliciously at the parts beneath, punctuating his mirth with moans. Dean’s hand was there, then, at his groin; but all he did was scritch his fingers lightly through the dark ruff of hair. Too soft, too much, too little, _perfect_...

Cas’ body shuddered upwards with a low, groaning cry. He grabbed at the pillow with one hand, Dean with the other. He was alight, inside and out, as the coiled pressure spiraled out in release. Sparking, tingling, so _warm_ , so _good_. Pulsing pleasure melted down into a haze of satisfaction.

His breath cycled in heaves as the feelings gradually dissipated. A corner of the sheet was being used to gently wipe him clean. When he opened his eyes, Dean was there, hovering over him on propped elbows, looking pleased. He leaned in for a kiss. Cas captured his lips eagerly and hummed. He threaded his synthetic fingers through Dean’s hair, enjoying the softness tufting between his fingers.

“That good, huh?” Dean asked with a laugh when they parted. Cas grabbed his shoulders and hauled him down again.

“So. Very. Good,” he breathed between kisses shaped by both his and Dean’s smiles.

“Maybe next time I’ll tie you down.”

A little thrill pulsed through Cas at the thought of the cuffs stashed under the four corners of the mattress. He wondered again about when, exactly, he’d unwittingly sold his soul to whoever was responsible for bringing Dean into his life. Or, whoever dropped _him_ into _Dean’s_ life, perhaps. He’d never really believed in God as any sort of divine orchestrator, but if the guy was out there, maybe Cas owed him some gratitude.

“Also,” Dean commented, flopping off to one side and lifting up the pen-sized wand. He held it up over his face, twirled it in his fingers. “This one’s called the _Tiny Teaser_. It’s the smallest one they make.”

Cas blinked at it, uncomprehending for a moment. “There are… stronger ones?”

“Mhmm.” Dean was smirking.

Heaving up, Cas rolled on top of him and grinned. “We’re going shopping.”


End file.
